I have converted an avi file, but the audio didn't work (tested on VLC and KMPlayer).
So, I extracted the audio stream separately and tried to mux it.
As a result, I have a video with two audio streams, where I can't hear anything on first stream (see Mediainfo extract).
I thought avi container can hold only one audio stream???

Stream 1 doesn't produce any audio playback. I can select the audio streams in a player, and only stream 2 has the good audio.

I take you don't need such a splitter to switch between the streams in MP4 or mkv container?

Further, I've tried to put some order in the streams. So I've tried to load it in Avidemux, but it crashed...
I've used another tool to extract the streams and mux the good audio with the video. Now I have only one video and one audio streams...

Audio track 1 didn't produce any sound at all, but it was the default output track in the first conversion.
I thought if I mux this video with a new track, then the existing track will be replaced. I was surprised to see them both in the avi container.

I've solved the issue using Avanti (Avidemux was crashing every time I tried to open the video).
Just extracted the video and muxed it with the good audio track from the original input file.

Thanks for the suggestion of avimux-gui. I'll keep that in reserve, if Avanti fails me in the future.